E. B. BLACK AND J. M. STENGLE 
455 
edge of bovine blood groups, and for that mat- 
ter of any animal blood typing system, may pro- 
vide an insight into evolutionary relationships 
between species and between breeds within a spe- 
cies. For example, a remarkable similarity exists 
between the blood grouping systems of cattle 
and of the American bison with homologies in 
not less than nine major blood types. On the 
basis of this observation, Stormont et al.^^ have 
suggested that domestic cattle and the Ameri- 
can Bison be classified as members of the same 
genus. In Europe, the blood factor Z', an allele 
of the bovine A system, occurs in a limited num- 
ber of breeds of cattle distributed in a pattern 
from Italy northward through France to south- 
ern England. The Z' allele is absent from 
Scandanavian32-34 g^^^ German^^ breeds but 
is seen in the Brahman breed of Asian origin. 
Not only does the distribution of the Z' indicate 
a genetic relationship between several geo- 
graphically separated breeds of cattle, it may 
well mark the progress of early man as he mi- 
grated from southern Asia to Europe taking his 
livestock with him. 
DOGS 
Although the dog has long been the principal 
research animal in many laboratories, its blood 
grouping systems have been studied less exten- 
sively than those of many other species includ- 
ing sheep and cattle. Seven major canine red 
cell antigens are recognized: A (subgroups Ai 
and A2) B, C, D, E, F, and G (Figure 7) . Each 
gene when present acts as a dominant factor^*' 
and, except in the A system, multiple alleles have 
not been identified. Naturally occurring recipro- 
cal antibodies are encountered only occasionally. 
As in cattle and sheep most canine blood group 
discovery has been accomplished using isoim- 
Antigen 
No. Dogs 
Tested 
Incidence 
(%) 
Antigen 
No. Dogs 
Tested 
Incidence (%) 
A 
954 
62.6 
D 
764 
22.3 
Subgroup A^ 
332 
44.6 
E 
231 
73.1 
Subgroup Aj 
332 
19 
F 
165 
99.4 (one animal 
negative) 
B 
867 
5.5 
G 
18 
» 
C 
947 
98.4 
Figure 7. — Major canine blood group antigens^^ 
munization techniques. The first recognition of 
blood groups in dogs was made by Von Dungern 
and Hirzfeld^^ almost 62 years ago with a de- 
scription of four blood types. In 1913 Ottenberg, 
Kaliski, and Friedman^^ reported the first trans- 
fusion reactions in dogs infused with incompat- 
ible canine blood. The phenomenon of isoim- 
munization in dogs infused with incompatible 
blood was first recognized in 1924 by McEnery, 
Ivy and Pechous.^'' Their observations, fol- 
lowed by similar observations of Melnick, 
Burack, and Cowgill''" and others,'*i-^° laid 
the foundation for the development of the 
modern canine blood grouping system. 
The canine A blood group, seen in about 63% 
of randomly sampled dogs, is from a scientific 
standpoint the most important of the canine 
blood systems. The A group is unique among 
canine blood types in that it exists in more than 
one grade of reactivity^^ and is apparently the 
only canine blood group which regularly fixes 
complement.^2 When erythrocytes from several 
A positive dogs are incubated in separate test 
tubes with several samples of anti-A antisera in 
the presence of complement, varying reactions 
are observed. In some tubes, various degrees of 
hemolysis occur and the cells which are not 
hemolyzed are agglutinated. In other tubes A 
positive cells are agglutinated ranging in degree 
from strong to weak with no observable hemol- 
ysis. In still other tubes red cells are neither 
agglutinated nor hemolyzed but become mark- 
edly reactive in the antiglobulin test. 
In 1952 it was suggested by O'Brien that type 
A cells which did not hemolyze when incubated 
with anti-A antisera in the presence of comple- 
ment in fact represented a subgroup of A anti- 
gen significantly different from the antigen 
associated with in vitro hemolysis. Soon there- 
after, an A positive dog whose red cells pro- 
duced only a strong agglutination reaction was 
immunized with type A red cells which reacted 
with complete hemolysis. An antiserum was 
produced which reacted only with those type A 
red cells which were hemolyzed to some extent 
when incubated with anti-A and complement 
and not with those which showed agglutination 
only. The subgroups of A proposed by O'Brien 
were then serologically distinguishable. Sub- 
group Ai included dogs having type A erythro- 
